In copending application Ser. No. 479,094, filed June 13, 1974, entitled "Hydraulically Operated Heavy Lift System for Vertically Moving a String of Pipe" and assigned to the same assignee as the present invention, there is described a lift system for raising and lowering a segmented string of pipe from the deck of a surface vessel. In the heavy lift system therein described, two linear lift units are spaced along the axis of the pipe string and are arranged to alternately engage spaced collars on the pipe and move the pipe string vertically in incremental steps. Each lift unit has a stroke equal to approximately half the distance between collars. One or the other of the lift units supports the entire load of the pipe string and associated subsea mining equipment attached to the end of the pipe string. Either lift unit therefore may be subject to loads of 9,000 or 10,000 tons. It is desirable therefore to provide some means to "park" the system so as to remove the load from the lift units during static hold conditions, as a safety backup in the event of operating failure of either the heavy lift units, and to make emergency repairs on the lift system. The parking brake must be integrated with the heavy lift units so that it can function to transfer the load from the heavy lift units to the parking brake in the event of any one of a number of failure conditions which might occur in the heavy lift system, such as when either one of the drive units won't move, or a load supporting element of either drive unit won't engage or won't release. It is also necessary in controlling the load supported by the pipe to be able to rotate the pipe to align the load in particular angular direction.